Evolutionary Dynamics, Evolutionary Forces, and Robustness: A Nonequilibrium Statistical Mechanics Perspective

Abstract

Any realistic evolutionary theory has to consider: (i) the dynamics of organisms that reproduce and possess heritable traits; (ii) the appearance of stochastic variations in these traits; and (iii) the selection of those organisms that better survive and reproduce. These elements shape the "evolutionary forces" that characterize the evolutionary dynamics. Here, we introduce a general model of reproduction-variation-selection dynamics. By treating these dynamics as a non-equilibrium thermodynamic process, we make precise the notion of the forces that characterize evolution. One of these forces, in particular, can be associated with the robustness of reproduction to variations. The emergence of this trait in our model--without any explicit selection for it--is an example of a general phenomenon, which can be called enaptation, distinct from the well-known and studied phenomena of adaptation and exaptation. Some of the detailed predictions of our model can be tested by quantitative laboratory experiments, similar to those performed in the past on evolving populations of proteins or viruses.